Hydroxyapatite being one kind of calcium phosphate is ceramics as a major constituent of a tooth or bone, and has excellent biocompatibility, protein adsorption characteristics, catalytic activity or the like, and therefore is used as a biomaterial such as an artificial bone and a bone prosthetic material, a packing material for chromatography or a catalyst for synthesizing polymer alcohol or the like. In particular, from viewpoints of biocompatibility, adsorption characteristics, reaction characteristics or the like, a porous hydroxyapatite material is further suited therefor. For example, when hydroxyapatite is used as the biomaterial, hydroxyapatite is made porous to allow a biotissue to penetrate into pores to facilitate bonding with the biotissue. Moreover, when hydroxyapatite is used as the packing material for chromatography or the catalyst, hydroxyapatite is made porous to allow an increase in a specific surface area to improve separation characteristics and the reaction characteristics.
Then, in order to produce a porous hydroxyapatite body, a proposal has been made on drying and calcining the resulting gel in a state in which the bubble are hold (see Patent literature No. 1, for example) by a method of stirring slurry of hydroxyapatite and a water-soluble polymer to bubble the slurry, and gelating the bubbled slurry by heating.
However, for example, in order to allow circulation in a blood flow to form a neonatal bone into an inside when the thus obtained porous body is used as the artificial bone, or in order to facilitate passage of a sample to improve a filtration rate when the obtained porous body is used as the packing material for chromatography, foam formed within hydroxyapatite needs to be open. However, the method of obtaining the porous body using the foam included in the slurry has problems of causing no sufficient mutual connection of the foam formed in the slurry to be high in a ratio at which the foam is formed as closed pores in the porous body, and low in a ratio at which open pores are formed. Moreover, control of the foam is difficult, and therefore the method has a problem of difficulty in controlling a uniform pore size and void ratio.
Moreover, a method is also known in which slurry of ceramics such as hydroxyapatite is impregnated into a porous organic body such as a sponge to dry and calcine the porous organic body into which the slurry is impregnated. According to the publicly known method, a ceramics porous body having a high ratio of open pores and a high void ratio can be produced (see Patent literature No. 2, for example).
However, porosity of the ceramics is specified by porosity of the porous organic body. Therefore, when an attempt is made on producing a porous ceramics body having finer pores, the slurry is filled in the porous organic body to cause clogging. As a result, such an attempt has a disadvantage of difficulty in producing a porous ceramics body having open micropores.